This is easily the most common question asked by newcomers to the RV lifestyle. The answer is simple: Pretty much every motorhome manufacturer makes/made a fine coach. There are no 'brands to avoid/look for'.
Coaches that are made by companies that are out of business are just as easy/hard to maintain as coaches with live company backing. Parts (other than perhaps body panels) are just as easy to come by. They all made their coaches out of the same off-the-shelf, easy to source materials.
In general, you want to look for a FLOORPLAN you like, then look for WATER DAMAGE and MAINTENANCE RECORDS. Remember, motorhomes are not like cars, low mileage does not necessarily mean low usage. For instance, you might find a coach with 12,000 miles on it that was lived in 24/7/365 for 10 years.
Once you find the coach with the magical combination (floorplan,condition,maintenance), PRICE is on the table.
Once you have narrowed the list of particular coaches you are interested in, have a look at the NADA RV GUIDE
to get a feel for price. Remember, the BUYER and the MARKET determines the worth of any item, not the seller. A seller that tells you how good a deal his coach is, doesn't understand this basic premise.
Right now, increasing fuel prices are likely to adversly affect the sellers position, however the start of 2012 camping season plays in his favor. You will find different market dynamics in play in different areas. Expand your search to include far-away locations.
Good luck, and once you have some candidates in mind, let us know and some actual owners of those coaches will likely chime in.